One known process for producing high quality aqueous sodium hypochlorite having low chlorate concentration uses certain ejectors, herein sometimes referred to as high-pressure ejectors, to inject NaOH solution into a chlorine gas stream passing through a mixing chamber. The pressure of the solution must be elevated to some superatmospheric pressure in order for the ejectors to work properly. Typical pressures are in the range of 50 psig-80 psig. Pumps are used to develop that pressure for forcing the caustic solution through and out of the ejectors.
Because the ejectors have venturis through which the liquid passes, the accelerating liquid flow creates vacuum that draws chlorine into the flow for mixing with the liquid. The effectiveness of the reaction between the NaOH and the chlorine depends to a significant degree on the turbulence that the ejectors impart to the mixture as it flows downward through the mixing chamber.
The process typically uses pure chlorine gas produced by electrolytic cells and then cooled to a desired temperature (35° C.-40° C. is typical). The cooled chlorine is saturated with water vapor. The pumps and ejectors add cost and complexity to an installation, and they require significant energy input for proper operation. If inert gas is present in the chlorine stream, it can degrade ejector effectiveness.
Increasing the pressure at which the ejectors inject caustic in order to maximize completeness of the reaction and thereby increase production efficiency ultimately leads to the generation of foaming (emulsification) in the liquid product being produced in the mixing chamber. Such foaming is seen to be detrimental to a continuous process. Furthermore, a process that seeks to produce high-strength bleach is more prone to foaming as bleach strength increases.